High spin polarization of tunnelling electrons at the interfaces in fullerene-magnetic metal systems

Sakai, Seiji; Matsumoto, Yoshihiro; Otomo, Manabu; Entani, Shiro; Avramov, P.; Naramoto, Hiroshi*; Fujikawa, Takashi*

In the present study, voltage-dependence of the TMR effect was investigated for the granular C-Co films with the current-perpendicular-to-plane geometry. It is revealed that the MR ratio conforms to the exponential MR-V relationship down to zero bias voltage. By considering the possible MR enhancement by higher-order cotunnelling, it is successfully demonstrated that the large TMR is attributed to the very high spin polarization (P = 0.8) of tunnelling electrons generated at the C-Co compound/Co interface. The ferromagnetic exchange coupling at the interface and the interlaryer electronic interaction are able to give rise to the high spin polarization in connection with the theoretically predicted spin-filtering effect of the C-Co compound.